Silo unloaders are operable to loosen forage material that is compacted within a vertical silo structure and remove the loosened forage material from the silo for feeding to animals. Silo unloaders are typically manufactured in two configurations. One configuration is fixed at the bottom of the silo and removes forage material from the bottom of the silo, while the other configuration is referred to as a top unloader in that the silo unloader apparatus is lowered from a storage position within the dome of the silo structure onto the top surface of the compacted forage material.
Top unloading silo unloaders are well known in the art as a method for removing silage from a vertical tower-like silo structure. Silage in the form of chopped feed or crop material, such as corn plants or hay, is loaded into the silo structure typically by blowing the silage material an opening at the top of the silo structure so that the silage material drops to the bottom of the silo and compacts by its own weight until the level of the silage material is near the top of the silo structure. Over time, the forage material loaded into the silo, ensiles and becomes a fermented feed material commonly referred to as silage. When removal of the silage from the silo is desired, such as to feed livestock, particularly cattle, the top unloading silo unloader is lowered from the storage position within the dome of the silo onto the top of the compacted silage material.
A typical example of a top unloading silo unloader can be seen in U.S. Pat. No. 5,642,977, granted on Jul. 1, 1997, to Gregg W. Hanson, et al. Such silo unloaders are mounted for rotation about a circular track. Near the center of rotation of the silo unloader is a blower that receives a supply of dislodged silage material and operates to blow the collected silage material into an opened door of the silo chute. An arm is connected to the sill of the opened door so that the discharge path of the blower is always aimed at the opened door. To collect silage from the top of the compacted supply of silage within the silo, the unloader is provided with an auger mechanism that extends substantially from the center of rotation to the periphery of the silo. This auger mechanism rotates around the silo on the circular track and delivers collected silage to the inlet opening of the blower.
The auger mechanism that collects the silage from the top surface of the compacted silage can be a double auger apparatus, as is disclosed in the aforementioned U.S. Pat. No. 5,642,977, or a single auger mechanism as is taught in U.S. Pat. No. 4,057,151, granted on Nov. 8, 1977, to Richard Weaver. Another configuration of a top unloading silo unloader can be seen in U.S. Pat. No. 4,465,409, granted on August 14, to Floyd E. Buschbom, et al. Other configurations, including both single and double auger silage collection devices, can be found in U.S. Pat. No. 3,968,998, issued to Johann Wolf on Jul. 13, 1976; in U.S. Pat. No. 4,772,173, issued to Floyd E. Buschbom, et al, on Sep. 20, 1988; and in U.S. Pat. No. 4,329,105, issued to Floyd E. Buschbom et al, on May 11, 1982. Each of these top unloading silo unloaders utilize a blower apparatus that uses a significant amount of energy to accelerate the collected silage material to be blown through the opened door of the silo chute for collection at the bottom of the silo structure.
Top loading silo unloaders generally have mechanisms which allow them to be placed within the round silo tower and then rotate or pivot about the center of the tower. Ideally, the auger arm will evenly cut through all of the silage and uniformly remove it from the silo. Because the auger mechanism is rotated around the center of rotation of the silo unloader, the silo unloader will not remove silage from only one side of the silo at a greater rate than the other side, thus creating an uneven or unlevel upper surface of the silage.
A number of things must happen as this auger arm rotates around the silo in order to effectively unload the tower silo. First, the auger arm must evenly remove and cut through the silage as it is removed, which can be difficult to accomplish when the silage is very hard due to either compaction or freezing. Secondly, silage must be evenly removed from the center point so as to avoid the creation of a mound or “plug” at the center or pivot point within the silo below the single auger blower. Also, silage must be removed right up to the walls, thus not leaving additional amounts of silage frozen to or attached to the walls.
Also important in the operation of a silo unloader are all the usual concerns regarding efficient operation (both from a power or energy consumption perspective and a silage transfer rate perspective). Typically, a farmer would like to move silage at a very high rate and use small amounts of power to do so. Also, as farms continue to get larger, it is very important for the farmer to remove silage at a higher rate as more livestock need to be fed.
Another common problem with the top mounted silo unloaders comes from the use of the closed cavity blower. Blowers typically used in silo unloaders are similar to any other fan or blower mechanism used in numerous material transfer situations. Generally, the blower has a rotating shaft with a number of blades attached thereto. The shaft and blades are configured within an enclosed cavity with an inlet port and outlet port. Silage is then fed into the inlet by the auger mechanism, usually through flipping blades or paddles. The silage is engaged by one of the blower blades and is propelled out the blower outlet port.
Particularly with single auger collection mechanisms, the auger draws material toward the center of the silo while advancing in the direction opposite the auger rotation. Situated at the center is the blower mechanism which is positioned such that silage is propelled into its inlet. The auger arm or auger assembly then rotates around the tower silo to evenly and uniformly unload material. As this entire mechanism rotates around, the enclosed bottom portion of the blower assembly tends to contact and compact the silage at the center of the silo. Furthermore, due to the alignment of the auger and transfer blades within the silo, this compacted material is not usually engaged by the auger. Therefore, a compacted mound is created which cannot be easily removed by the silo unloader.
In summary, the single auger collection mechanism has been underutilized in favor of the double auger collection mechanism to provide greater aggressiveness to break up compacted or frozen silage, and to prevent the creation of a compacted mound or hill at the center point of the silo under the blower. However, the use of a double auger collection mechanism is more expensive to manufacture as a greater amount of material and labor is required to form two augers instead of a single auger.
Nevertheless, the double auger collection mechanism does provide some advantages in operation over the single auger configuration. The double auger mechanism is desirable in removing compacted or frozen silage as the two augers can work in conjunction with one another to very aggressively break up the silage. Usually, the two augers will be placed parallel one another and will be configured to rotate in opposite directions in collecting the silage material. By rotating in opposite directions, the augers will not tend to pull the auger arm in any specific direction. Stated alternatively, the pulling forces created by the rotation of each auger will tend to cancel out one another. Further, the two augers can be sized differently so as to cut at different depths, which creates more efficiency because each auger is attempting to shave off only a limited amount of material thus allowing the second auger to cut a little deeper. Conversely, the double auger collection mechanism can be too aggressive during operation and has a tendency to pull the unloader apparatus off center.
However, not all silo structures are provided with a vertical chute along the side of the silo structure provided with a plurality of vertically spaced doors through which the collected silage can be blown for collection at the bottom of the chute. Some silos are formed with a central discharge chute, as is disclosed in U.S. Pat. No. 5,112,180, issued on May 12, 1992, to Richard M Hough, for which a rotating scraping mechanism is provided to collect silage from the compacted supply around the central discharge chute. The scraper mechanism moves the silage through openings in the central discharge chute as the mechanism is rotated. The scraper mechanism is suspended by cables from the top of the silo and can operate on demand until the silo is ultimately emptied.
Another silo configuration is disclosed in U.S. Pat. No. 3,980,186, granted on Sep. 14, 1976, to Duane A. Leith, in which the discharge chute is formed along the inside of the silo by a semi-circular member that keeps silage material from being placed along the formed discharge chute. As silage material is loaded into the silo structure during harvest time, the silage handling apparatus is winched upwardly to stay on top of the silage material being loaded. As a result, the compacted silage maintains a formed chute along the inside of the silo as created by the semi-circular member. When collection of the compacted silage material is desired, the silage handling apparatus is rotated to scrape silage material off of the top surface and then move the collected silage material into the formed discharge chute.
Further complicating the use of blower-type silo unloaders is the tendency for silos to be constructed in larger, greater diameter configurations. Where silos having a diameter of twenty feet are easily adaptable to having a blower move collected silage to an open chute door, larger diameter silos, particularly silos that can be built in the range of a forty foot diameter configuration, present too great of a distance for forage to be accurately and efficiently blown along a trajectory that will effectively hit the open door to the discharge chute. Accordingly, an improved top mounted silo unloader would be desirable so that larger diameter silos can be constructed without the limitations of the unloading apparatus restricting the effective size.
Bulk material conveyors also utilize an auger collection mechanism, in either single auger or double auger configurations, such as is disclosed in U.S. Pat. No. 4,230,221, granted to Isaac Beresinsky on Oct. 28, 1980, showing a single auger collector, and in U.S. Pat. No. 4,890,721, granted to Tadayoshi Kamiwaki on Jan. 2, 1990, showing a double auger collector. These bulk material conveyors incorporate a pair of opposing, material clamping, juxtaposed conveyor belts that receive the bulk material discharged from the auger collector between the opposing conveyor belts to elevate the bulk material vertically and then horizontally for discharge to a remote location.
It would be desirable to provide an improved top mounted silo unloader that would overcome the disadvantages of the prior art silo unloaders and provide an effective silage unloading capability that will enable the construction of larger diameter silo structures.